Sean's gift/curse is that he can fight comfortably at his pace for 5 rounds. Excellent defense, solid jab, solid front kick and a decent 1-2. That is his whole game and he doesn't really change it based on who he's fighting. It looks like hard sparring and its in a really specific rhythm.
When he picked up the pace nearing the end of round 5, he was getting out of position. If he fought DDP like that when they were both fresh, he probably gets knocked out.
He'll beat unranked guys like the two he fought before Izzy and win, but he'll have a lot of split stinkers like Cannonier and Driccus against named opponents.